Conventionally, the packing apparatus as fundamental has been proposed in the U.S. Pat. No. 4,144,697 by the inventor of the present invention, which comprises means for making a band of film tubular lengthwise in sequence, and means for feeding articles to the tubular-film-making means at regular intervals, means at the downstream side of the tubular-film-making means and for cutting the film between the respective trays, suction means which uses an air flow to suck downwardly both ends of tubular film at both sides of tray, roller means having an opening in part and for folding the upstream side end of tubular film toward the bottom surface of each tray, and means for folding the downstream side end of the tubular film toward the bottom surface of each tray. In detail, the packing apparatus disclosed in the U.S. Pat. No. 4,144,697 conveys the trays in the tubular film continuously on an air suction channel so that both ends of the tubular film are stretched downwardly by suction applied to both ends and caught by the predetermined hook element to be folded toward the bottom surface of each tray. Such method requires the air suction channel larger in length to lead to a larged-sized apparatus. In order to solve this problem, a method is proposed which conveys the trays intermittently to cut the film during the stop and then both ends of the cut film are taken in the lower air suction channel and folded downwardly simultaneously with starting of transportation of the trays. Such method can reduce the air suction channel in length to miniaturize the apparatus, but the packing capability is small and also the suction by air is insufficient to stretch the film ends. For example, sliced-meat products are mostly reinforced by the trays and a thermoplastic film merely covers the upper opening of tray 2 as shown in FIG. 14 and also is made as thinner as possible from the economical view-point. This kind of film becomes larger in the frictional property as it is extended so that both ends 3a and 3b of film folded onto the bottom surface of tray are easy to stick naturally thereon even without heating. Some films are extensible even by 300% and the film as thinner as possible is used so that if the film is insufficiently extended to cover the tray, the film is slackened above the tray even with a minute temperature change and hinders the transparency of film, thereby not making the articles presentable.
Therefore, it is required that the trays are continuously transported without lowering the packing capability therefor and also the film is not only pulled by air suction but also mechanically extensible.